One of the main threats in the DVD world is the mass production of pirate copies of DVDs, which are distributed in black markets. The digital nature of DVDs makes it possible (and usually easy) to create perfect copies of content distributed on DVDs, including the associated control data (such as, for example, encryption keys used in encrypting data on the DVDs), thus bypassing other security mechanisms and obtaining a copy in the same quality as the original. A copy made in such a way is referred to herein as a “bitcopy”.
There is a clear need in the DVD industry for security mechanisms which will prevent the above-mentioned scenario, or at least make it substantially more difficult to create such copies.
It is appreciated that the above-mentioned problem is not limited to DVDs, but holds also for other types of storage media.
Typically content is pre-recorded on one storage device and distributed to the markets, and writers (authorized or non-authorized) may copy the content to a blank storage device. If appropriate countermeasures are not taken, authorized players will not have the ability to tell the difference and will play the content from the copied storage device.
A company named Doc-Witness Ltd., 8 Hamelacha Street, Rosh-Ha'ayin 48091, Israel, has published a white paper which describes a product, marketed as OpSecure, which comprises adding a photo detector, chip, LED power source, and PCB (Printed Circuit Board) to storage media in the DVD format to secure the content within. The OpSecure product's description is available on the World Wide Web at:
www.doc-witness.com/whitepaper.html.
A PhD thesis titled “Physical One-Way Functions” by Pappu Srinivasa Ravikanth of MIT, describes a physical device for implementing one-way functions, the device being referred to throughout the present specification and claims as a “bubble token”. The bubble token is a 3D plastic token filled with air bubbles. When a laser beam is directed onto the bubble token, it creates a unique 2D light pattern on a receiver which is located on a side of the token opposite to the laser beam. The thesis is available on the World Wide Web at:
web.media.mit.edu/˜pappu/htm/pubs/PappuPhDThesis01.pdf.
A white paper describing an industry standard proposed by Intel, IBM, Matsushita and Toshiba for Content Protection for Pre-recorded Media (CPPM) is available upon request from the 4C entity on the World Wide Web at:
www.4 centity.com/tech/cprm.
A white paper describing an Advanced Access Content System (AACS) is available on the World Wide Web at:
aacsla.org/media/aacs_technical_overview—040721.pdf.
A symmetric encryption scheme called CSS (Content Scrambling System) is described, for example, in Taylor, J., “DVD Demystified”, McGraw-Hill (2000) Second Edition, pp 192-193. Such an encryption scheme is used for encrypting data on DVDs.
A description of the AES (Advanced Encryption Standard) is available at: csrc.nist.gov/publications/flps/fips197/fips-197.pdf.
PCT Patent Application WO 99/38162 of NDS Limited (and corresponding UK Patent GB 2 338 586 to NDS Limited and U.S. patent application Ser. No. 09/376,384 of Bar On et al.) entitled “Protection of data on media recording disks” describe securing transfer of information between a media recording disk and a media recording disk player by means of an electronic security chip attached to the media recording disk, the chip communicating with the disk player via encrypted communication.
The disclosures of all references mentioned above and throughout the present specification, as well as the disclosures of all references mentioned in those references, are hereby incorporated herein by reference.